1. Field of the Invention
The present invention relates to an optical disc unit with an optical disc loaded therein for recording or reproducing information.
2. Description of the Related Art
An optical disc unit, with an optical disc loaded therein, if for allowing laser beam to be incident on an information recording surface of the optical disc to record information onto the information recording surface or reproducing the recorded information.
FIG. 6 is a perspective view of a conventional optical disc unit 100. The optical disc unit 100 is mainly made up of a generally rectangular chassis 101 formed by sheet metal working and having cutout portions formed partially in its outer edge, a spindle motor 103 mounted on the chassis 101 and with a turntable 102 fixed thereto coaxially, guide shafts 104 and 105 disposed in parallel with each other, an optical pickup 106 disposed between the guide shafts 104 and 105, provided with an objective lens 106a and having a generally rectangular external form, and a feed mechanism for feeding the optical pickup 106 in the longitudinal direction of the guide shafts 104 and 105, which feed mechanism will be described later.
Now, a detailed description will be given below about the construction of the optical disc unit 100.
First, centrally of the chassis 101 is formed a generally square hole 101a. On one of edge sides of the hole 101a opposed to each other in the longitudinal direction of the chassis 101, the spindle motor 103 is mounted and fixed onto the surface of the chassis 101. In the hole 101a, on both transverse sides of the chassis 101 are disposed guide shafts 104 and 105 which extend longitudinally of the chassis. One end portion on the turntable 102 side of the guide shaft 104, which end portion will hereinafter be referred to simply as xe2x80x9cone end portion of the guide shaft 104,xe2x80x9d is positioned in both longitudinal and radial directions by positioning pieces 101b and 101c which are formed by projecting and bending a part of the chassis 101, and is mounted and fixed to the chassis with screw 107. An opposite end portion of the guide shaft 104 is also positioned by a positioning piece 101d and is urged to the chassis 101 elastically by means of a plate spring 108 as an elastic member fixed to the chassis 101 with screw 111, and is supported thereby. On the other hand, both end portions of the guide shaft 105 are also positioned by positioning pieces 101e, 101f, and 101g, 101h, respectively, and are urged to the chassis 101 elastically by means of plate springs 109 and 110 as elastic members fixed to the chassis 101 with screws 112 and 113 and are supported thereby.
The guide shaft 104 is inserted through circular holes 106e and 106f formed in bent pieces 106c and 106d, respectively, which are provided at one longitudinal end of the optical pickup 106, and a cutout slot 106h formed in a bent piece 106g which is provided at an opposite end portion opposite to the circular holes 106e and 106f, is supported slidably by the guide shaft 105, whereby the optical pickup 106 is guided movably in the longitudinal direction of the guide shafts 104 and 105 (radially of the optical disc).
In order for an optical axis of the objective lens 106a of the optical pickup 106 to extend in a direction orthogonal to the information recording surface of the optical disc (not shown), the opposite end portion of the guide shaft 104 is moved in H1 direction nearly perpendicular to the surface of the chassis 101, while both end portions of the guide shaft 105 are moved in H2 and H3 directions respectively, and the guide shafts 104 and 105 are inclined for adjustment relative to the surface of the chassis 101, whereby the posture of the optical pickup 106 can be changed. Regarding how to adjust the guide shafts 104 and 105, it will be described later.
At one end portion on the bent pieces 106c and 106d side of the optical pickup 106 a nut member 114 is mounted integrally with the optical pickup and a nut portion 114a thereof is elastically urged and locked to a thread root of a lead screw 115 which is disposed substantially in parallel with the guide shaft 104 and rotatably about an axis thereof. On the other hand, to an end portion of the lead screw 115 on the side opposite to the turntable 102 is fixed a spur gear 116 coaxially for integral rotation with the lead screw. Further, a spur gear 117, which is in mesh with the spur gear 116, is fixed onto a rotary shaft of a feed motor 118. With rotation of the feed motor 118, the lead screw 115 rotates at a gear ratio determined by both spur gears 116 and 117 and the optical pickup 106 with the nut member 114 fixed thereto is fed radially of the optical disc.
The optical disc is put on the turntable 102 and is rotated by the spindle motor 103. Laser beam emitted from the objective lens 106a of the optical pickup 106 is focused onto the information recording surface of the optical disc and a return beam which has been reflected in accordance with information from the information recording surface passes through the objective lens 106a and is received within the optical pickup 106, whereby information can be read or recorded to or from the information recording surface of the optical disc. Following the information recording surface of the optical disc, the optical pickup 106 is controlled longitudinally of the guide shafts 104 and 105.
Now, with reference to FIG. 7, the following description is provided about how to adjust the inclination of the guide shafts 104 and 105. FIG. 7 is a sectional view taken on line 7-7 in FIG. 6.
As shown in FIG. 7, at the position of the opposite end portion of the guide shaft 105 which is urged by the plate spring 110, a downwardly projecting recess 101i is formed in the chassis 101. Below an abutment face of the plate spring against the guide shaft 105 and centrally of the recess 101i, an adjust screw 119 is disposed rotatably so as to project from below to above the chassis 101. The opposite end portion of the guide shaft 105 is put on a tip end face 19a of the adjust screw 119 which is disposed beforehand at a predetermined height. Further, with the right-hand side in the figure of the guide shaft 105 abutted against an abutment face 101hxe2x80x2 of the positioning piece 101h see FIG. 6), an urging face 110a of the plate spring 110 urges the guide shaft 105 obliquely, whereby the opposite end portion of the guide shaft 105 is urged and supported elastically by both screw tip end face 119a and abutment face 101hxe2x80x2.
In this construction, by turning the adjust screw 119, the opposite end portion of the guide shat 105 moves in H3 direction in the figure. More specifically, if the adjust screw 119 is turned clockwise, the opposite end portion of the guide shaft 105 can be adjusted to an upward H3xe2x80x2 direction, while if the adjust screw is turned counterclockwise, the opposite end portion of the guide shaft can be adjusted in a downward H3xe2x80x3 direction.
The above construction illustrated in FIG. 7 also applies to the positions of the other plate springs 108 and 109. Adjust screws disposed at the positions of the plate springs 108 and 109 are here identified by numerals 120 and 121, respectively. With this construction, the posture of the optical pickup 106 can be adjusted by turning the adjust screws 119, 120 and 121 and thereby changing the inclination of the guide shafts 104 and 105. For example, with reference to FIG. 6, if the adjust screws 119 and 121 (the positions of the plate springs 110 and 109, respectively) are turned at the same angle in the same direction and if both end portions of the guide shaft 105 are thereby moved the same distance in the same H3xe2x80x2, H2xe2x80x2 direction (upward) or H3xe2x80x3, H2xe2x80x3 direction (downward), the cutout slot 106h of the optical pickup 106 engaged with the guide shaft 105 also moves the same distance upward or downward, so that the optical axis of the objective lens 106a can be changed its angle relative to the direction (tangential direction) orthogonal to the radial direction of the optical disc.
If the adjust screws 119 and 120 the positions of the plate springs 110 and 108, respectively) are turned at the same angle in the same direction and the opposite end portions of the guide shafts 104 and 105 on the side opposite to the turntable 102 are thereby moved the same distance in the same H3xe2x80x2, H1xe2x80x2direction (upward) or H3xe2x80x3, H1xe2x80x3 direction (downward), the whole of the optical pickup 106 engaged with the guide shafts 104 and 105 tilt, whereby the optical axis of the objective lens 106a can be changed its angle relative to the radial direction of the optical disc.
In the conventional optical disc unit 100, however, when a shock is imposed on the optical disc 100 in transit for example, the guide shafts 104 and 105 may be displaced against the urging force of the plate springs 108, 109 and 110 and become disengaged from the chassis 101. To avoid this inconvenience, it has so far been necessary to use such plate springs 108 to 110 as afford an urging force sufficiently larger than the urging force required for the guide shafts 104 and 105 to be supported without any problem in normal use (during recording or reproduction of the optical disc) of the optical disc unit 100. Therefore, for preventing the chassis 101 from being deformed with a large urging force at the time of mounting and fixing the plate springs 108 to 111 to the chassis with use of screws 111 to 113, it is necessary to use a relatively thick sheet metal for the chassis, with consequent increase of cost.
Moreover, for increasing the urging force for the guide shafts 104 and 105, it is necessary to enlarge the plate thickness of the plate springs or increase the area to widen the area of contact with the guide shafts 104 and 105, thus also resulting in increase of cost.
Further, since it has so far been necessary that the mounting work for the plate springs 108 to 110 be done against a large urging force, a large force is required for holding the plate springs 108 to 110 at their mounting positions for the surface of the chassis 101; besides, the tightening torque for the screws 111 to 113 increases, thus leading to deterioration of the working efficiency.
Although in the above prior art plate springs were used as elastic members, there arise the same problems as above also in case of using coiled springs. Further, although the chassis 101 is constituted by sheet metal, there occur the same problems as above also in case of using a resinous chassis.
It is an object of the present invention to provide an optical disc unit capable of diminishing the urging force of elastic members used, capable of preventing the disengagement of guide shafts, capable of attaining the reduction of cost, and further capable of improving the working efficiency.
For solving the above-mentioned problems, in one aspect of the present invention there is provided an optical disc unit comprising a turntable on which an optical disc is placed, an optical pickup for recording or reproducing information to or from the optical disc, a guide shaft for guiding the optical pickup radially of the optical disc, and support means for supporting both end portions of the guide shaft, the turntable, the optical pickup, the guide shaft, and the support means being disposed on a chassis, at least one of the support means being provided with a rest surface for resting the guide shaft thereon, an elastic member for urging the guide shaft elastically, a restricting portion spaced a predetermined gap from the guide shaft, and adjusting means for moving the rest surface within the gap.
In another aspect of the present invention, the support means include a resinous support member for supporting the guide shaft, the support member being formed in the chassis by outsert molding and being provided with the restricting portion.
In a further aspect of the present invention, the restricting portion is a part of the support member, and the guide shaft is disposed in the gap by a snap motion of the restricting portion.
In a still further aspect of the present invention, the restricting portion comprises a pawl piece and a support piece for supporting the pawl piece, the pawl piece having a restriction face which defines the gap and a slant face against which an end portion of the guide shaft comes into abutment.
In a still further aspect of the present invention, the elastic member is a torsion coil spring, one end portion of the torsion coil spring being anchored to the chassis and an opposite end portion thereof urging the guide shaft.
In a still further aspect of the present invention, an opening for disposing the torsion coil spring therein is formed in the chassis at a position close to the support means, the opening having an engaging portion along an edge thereof for fitting therein of the torsion coil spring.